JPH06122934A - Aluminum alloy sheet excellent in formability and its production - Google Patents

Abstract

PURPOSE:To produce an aluminum alloy sheet excellent in formability and to provide its producing method. CONSTITUTION:This aluminum alloy sheet excellent in formability is the one obtd. by applying lubricating surface coating on an aluminum alloy sheet contg., by weight, 3 to 10% Mg and total 0.3 to 2.0% impurity elements of Fe and Si and having <=0.11 sliding resistance. An aluminum scrap contg. total 0.3 to 2.0% impurity elements of Fe and Si is used as a raw material, which is melted, and its components are regulated. After that, the content of Mg is regulated to 3 to 10%, and it is subjected to ordinary casting, is hot-rolled, is thereafter cold-rolled at 20 to 50% draft, is subjected to continuous annealing and is furthermore applied with lubricating surface coating to regulate its sliding resistance into <=0.11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy sheet suitable for an automobile body sheet and a method for producing the same, and particularly to provide an aluminum alloy sheet having good formability at low cost.

[0002]

2. Description of the Related Art Recently, in order to reduce the weight of automobile bodies, it has been studied to use aluminum alloy sheets as body sheets. Therefore, the aluminum alloy sheet is required to have excellent press formability and high strength as in the case of the conventional cold-rolled steel sheet. In order to meet such requirements, an aluminum alloy material of Al-Mg type 50 is used.
00 series alloys, more specifically, 5052 and 5182 alloys are used. However, in these alloys, the r value, which is an index of their ductility and deep drawability, is much lower than that of steel sheets,
It is difficult to form the same as a steel plate, and the parts used are limited to lightly processed parts such as hoods.

[0003]

As described above, various efforts have been made to improve the moldability, which has been conventionally low. For example, JP-A-61-130452 and JP-A-03-28
As described in No. 7739, a manufacturing method has been developed in which the upper limit of the amount of Fe and Si is regulated and, at the same time, high Mg is added to improve the elongation value. As described above, in both the conventional 5000 series alloy and the newly developed high ductility alloy, it is essential to use 99.7% or more of high purity new ingot as the ingot due to the purity regulation for securing the elongation value. It was It is well known that new aluminum ingot is expensive, and the elongation value of the aluminum alloy sheet according to the above-mentioned prior art manufactured by adding a high amount of Mg to this expensive new ingot is 40% or less. Remarkably lower than the elongation value of over%. In other words, the cost performance of aluminum alloy sheet is much lower than that of steel sheet.

Therefore, it is an object of the present invention to provide an aluminum alloy sheet having excellent formability and a method for producing an aluminum alloy sheet having excellent formability without using expensive new metal.

[0005]

DISCLOSURE OF THE INVENTION As a result of various investigations, the present inventors have improved the cost performance of an aluminum alloy sheet, that is, a new manufacturing method which provides an aluminum alloy sheet having good workability at low cost. I found a way. That is, in the present invention, Mg is contained in an amount of 3 to 10 wt%, F
e, having a lubricious surface coating on an aluminum alloy plate containing a total of 0.3 to 2.0 wt% of impurity elements of Si,
Provided is an aluminum alloy plate having excellent formability, which has a sliding resistance of 0.11 or less.

Further, according to the present invention, an aluminum scrap containing a total of 0.3 to 2.0 wt% of Fe and Si impurity elements is used as a raw material, and the amount of Mg after melting and adjusting the components is 3 to 1
0 wt%, normal casting, hot rolling, cold rolling with a reduction rate of 20 to 50%, continuous annealing, and a lubricious surface coating to reduce the sliding resistance to 0.11 or less. The present invention provides a method for producing an aluminum alloy plate having a good formability.

[0007]

The present invention will be described in more detail below. First, the reasons for limiting the chemical components in the present invention will be described. In addition, the content of components was set to wt%.

Mg: The aluminum alloy targeted by the present invention is an Al-Mg type alloy containing 3 to 10 wt% of Mg, and the strength of the material is mainly brought about by the solid solution strengthening mechanism of Mg atoms. Proportionately high strength is obtained while elongation is also increased. However, the amount of Mg is 3 wt%
If it is less than the above range, the strength required for a vehicle body panel cannot be obtained, and at the same time the elongation is low, so that the required formability cannot be obtained even if a lubricating treatment described below is combined. Thus, from the viewpoint of strength and formability, the larger the amount of Mg, the more preferable, but 10 wt.
Addition in excess of 5% deteriorates hot workability, making plate production difficult. For the above reason, the Mg content range is 3 to 10
It was set to wt%.

Impurity amount: Fe-Al-based and Mg-Si-based intermetallic compounds are factors that deteriorate the elongation of Al-Mg-based alloys.
It has been desired to suppress such elements as impurities as low as possible. Therefore, high-purity bullion is usually used, but the cost is increased because the bullion is expensive. Therefore, in order to reduce the cost, the present invention considered using recycled scrap as metal. F with constant amount of Mg
When the amount of impurities of e and Si is increased, the elongation value, which is a representative index of formability, sharply decreases as shown in FIG. 1, and as a result, as shown in FIG. The flange diameter also increases and the formability deteriorates significantly. As described above, it has been generally considered impossible to obtain a material that can withstand complicated molding such as an automobile body when using a low-purity material such as scrap. However, it is possible to produce an aluminum alloy sheet having sufficient formability even with a low-purity material as shown in FIG. 2 by combining with the technique described below. As shown in FIG. 2, the amount of impurities is 2 w
If it exceeds t%, the formability is deteriorated compared to the conventional material made of new metal even if lubrication is applied, so the upper limit of the total amount of impurities of Fe and Si is set to 2 wt%. In order to obtain better formability, it is naturally preferable that the amount of impurities is small, but considering the cost of scrap metal, the lower limit is 0.3w.
It was set to t%. Further, in order to achieve the usual moldability of high purity by the lubrication treatment, the elongation of the material is preferably 20% or more.

Lubricant Coating: Lubricant coating is another important requirement that constitutes the present invention. As shown in FIG. 2, it is possible to significantly improve the formability by imparting lubricity to a material that cannot withstand press forming when it is bare. Lubrication is achieved by resin coating. The resin may be either a film-removing type such as wax or a non-film-removing type of an organic resin such as an epoxy resin containing wax, but a non-film-removing type that allows welding coating as it is rather than a film-removing type that requires degreasing treatment after press molding. The type is preferable when considering the manufacturing process of the vehicle body. It is necessary to select the kind and the film thickness of these resins so that the sliding resistance μ at the time of plane sliding becomes 0.11 or less as shown in FIG. That is, the amount of impurities is 1.5 wt
%, The sliding resistance μ was set to 0.11 or less as a limit for improving the formability of the material to the same extent as the formability of the material using the conventional new metal (without a lubricating coating). Preferable examples of the lubrication coating include organic resins such as epoxy and epoxy-urethane series which have a chromate coating as a base and contain a wax.

Cold rolling reduction: When the amount of impurities is large, the amount of intermetallic compounds inevitably increases, which deteriorates the crystal grain growth during annealing after cold rolling, resulting in fine crystal grains in the product. . The elongation value of the material has a correlation with the crystal grain size as shown in FIG. 4, and the elongation increases as the grain size increases. Therefore, in order to improve the elongation of the low-purity material used in the present invention as much as possible, it is desirable that the cold rolling reduction rate is set to 20 to 50%, which is lower than usual, to achieve crystal grain growth. It should be noted that the production of the aluminum alloy sheet of the present invention may be carried out by a conventional method except for the cold rolling reduction.

[0012]

EXAMPLES The present invention will be specifically described below based on examples. (Example) With the amount of Mg fixed at about 5.5%, the amount of impurities (Fe
+ Si%) is changed in the range of 0.1 to 2.5%, the aluminum alloy is subjected to normal hot rolling, then cold rolling at a reduction rate of 30 to 40%, and annealed at 500 to 550 ° C for a short time. , Some materials were coated with resin. The tensile properties and cup moldability of these materials were investigated. FIG. 1 shows the relationship between the elongation value of the material without resin coating and the amount of impurities as it is annealed, and FIG. 2 shows the relationship between the cup moldability and the amount of impurities. In the resin coating material shown in the figure, a urethane-epoxy resin containing 10% by weight of wax was applied in an amount of 0.3 to 0.5 g / m ² . Further, cup moldability was evaluated by applying a low-viscosity oil to a 95 mmφ blank plate, molding with a 50 mmφ flat head punch, and measuring the flange diameter at break. It is clear that the resin coating significantly improves the moldability even if the amount of impurities is large and the elongation is low.

Next, the amount of impurities (Fe + Si) 1.5 wt%
Then, the above-mentioned resin was applied to a 5.5 wt% Mg-added aluminum alloy material while changing the basis weight (0.01, 0.4, 1 g / m ² ) and the flatness and cup formability were examined. The relationship between the two is shown in FIG. The figure also shows the formability level of a normal 5182 alloy (impurity content <0.3 wt%, 4.5 wt% Mg content). The sliding resistance μ decreases as the resin thickness increases, and as a result, the moldability improves. Conventional alloy 5182
A moldability similar to that is obtained when μ is about 0.11.

FIG. 4 shows the effect of the cold rolling reduction rate on the crystal grain size and elongation of a material having an impurity amount of 1 wt%. The annealing after cold rolling was 530 ° C. for 10 seconds, and the plate thickness after cold rolling was all 1 m.
The thickness of the hot rolled material was changed so that the thickness was m. As is clear from the figure, when the cold rolling reduction is 20 to 50%, the grain size becomes large and at the same time the elongation also increases.

[0015]

The aluminum alloy sheet manufactured by the method described in detail above uses inexpensive scrap as a raw material, and therefore has a much lower cost than the conventional aluminum alloy sheet and has a formability equal to or higher than that of the conventional material. Therefore, it is an optimum material for automobile bodies intended for mass production.

[Brief description of drawings]

FIG. 1 is a diagram showing the influence of the amount of impurities on the elongation of an aluminum alloy plate.

FIG. 2 is a diagram showing the influence of the amount of impurities and the coating of a lubricating resin on the cup formability of an aluminum alloy plate.

FIG. 3 is a diagram showing the effect of sliding resistance μ on the cup formability of an aluminum alloy plate.

FIG. 4 is a diagram showing the effect of cold rolling reduction on the elongation and average crystal grain size of an aluminum alloy plate.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshihiro Matsumoto 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki Steel Corporation Technical Research Division (72) Inventor Makoto Imanaka Kawasaki, Chuo-ku, Chiba-shi, Chiba Town No. 1 Kawasaki Steel Co., Ltd., Technical Research Division (72) Inventor Takaaki Hira No. 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Steel Co., Ltd., Technical Research Division (72) Inventor Naoki Nishiyama Chiba 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Japan Inside Kawasaki Steel Corporation Technical Research Headquarters (72) Inventor Yoichiro Togitsu 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Inside Furukawa Aluminum Co., Ltd.

Claims (2)

[Claims] 1. An aluminum alloy plate containing Mg in an amount of 3 to 10 wt% and Fe and Si impurity elements in an amount of 0.3 to 2.0 wt% in total has a lubricious surface coating and a sliding resistance of 0.
An aluminum alloy plate having excellent formability, which is 11 or less. 2. The total sum of Fe and Si impurity elements is 0.3 to
Aluminum scrap containing 2.0 wt% was used as a raw material, the amount of Mg was adjusted to 3 to 10 wt% after melting and composition adjustment, and ordinary casting and hot rolling were followed by cold rolling at a reduction rate of 20 to 50% and continuous annealing. A method for producing an aluminum alloy sheet having good formability, which comprises applying a lubricous surface coating to a sliding resistance of 0.11 or less.